The appeal for some old-fashioned savoir-vivre clearly touched a nerve around the world. Within hours, the story went viral on Twitter.

The manager, Fabrice Pepino, said he had not yet had to enforce the politeness policy, and admitted the sign was more of a gentle reminder than a serious threat.

“It started as a joke because at lunchtime people would come in very stressed and were sometimes rude to us when they ordered a coffee,” said Pepino. “It’s our way of saying, ‘Keep calm and carry on.’”

He added, “Most of my customers are regulars and they just see the funny side and exaggerate their politeness, but people are more relaxed now, and they’re smiling more. That’s the most important thing.”